Recent scientific studies and reports have indicated a preference for bicarbonate hemodialysis over acetate dialysis. An article published in asaio Journal, Volume 6, July/September, 1983 by Antonia C. Novello and Carl M. Kjellstrand entitled "Is Bicarbonate Dialysis Better than Acetate Dialysis?" reviews the history of the two types of dialysis and concludes that there is considerable evidence that bicarbonate dialysis is preferable in terms of patient tolerance. This article stops short of recommending a full-scale switch from acetate to bicarbonate dialysis because of the great cost involved in doing so, and recommends further study of the problem.
Another article in Vol. XXVII Trans Am Soc Artif Intern Organs, 1981, pages 655 through 658, entitled "Panel Conference Acetate Versus Bicarbonate in Dialysis" includes the statement
"Bosch notes that during acetate dialysis, a considerable number of patients have experienced a fall in blood pressure associated with such systems as weakness, nausea and vomiting. Hemodynamic studies have shown that during acetate dialysis the removal of fluid by ultrafiltration induces a fall in cardiac output. Total peripheral resistance does not change and consequently blood pressure falls. On the other hand, when quantitatively similar fluid removal during bicarbonate (dialysis) induces a comparable fall in cardiac output, peripheral resistance increases so blood pressure does not fall as much. Bicarbonate dialysis is thus tolerated better."
Other studies have similarly concluded that a return to bicarbonate dialysis as a preferred treatment is desirable if certain practical and economic problems can be satisfactorily solved. Not the least of these problems concerns the long term storage of bicarbonate dialysate. Presently, such solutions when used in dialysis systems must be disposed of at the end of each day. The instability of bicarbonate dialysate due to decomposition of HCO.sub.3 into CO.sub.3 and CO.sub.2 which is lost into the atmosphere results in a decline in HCO.sub.3 and increased dialysate pH. As a result, the stability of the solution can be maintained over a very brief storage period only.
The objective of the present invention is to deal directly with the problem of increasing the storage life of bicarbonate dialysate to such an extent that it will become feasible to use the medically preferred solution in kidney dialysis and to use it more economically than the less preferred acetate dialysate. In particular, the present invention seeks to increase the storage life of bicarbonate dialysate from one day to approximately thirty days. With this possibility realized through the present invention, the cost of using bicarbonate solutions for dialysis is reduced from $3.00-$4.00/gallon/treatment to $0.14/gallon/treatment. This renders the use of bicarbonate dialysate less costly than the use of acetate dialysate, in accordance with a further object of the invention.